Supplemental fuel system for exhaust gas recirculating system

ABSTRACT

A carburetor is supplied with an additional fuel and air channel connected to the engine intake manifold past a movable valve that opens the channel only when exhaust gases are being recirculated into the engine so that engine driveability is improved. The valve is sensitive to the movement of a second valve controlling the recirculation of the exhaust gases as a function of throttle valve movement.

United States Patent Aquino et al. Sept. 9, 1975 SUPPLEMENTAL FUELSYSTEM FOR 2.047.743 7/1936 Moore 123/119 A EXHAUST GAS RECIRCULATINGSYSTEM 2,()87,l l6 7/1937 Prentiss l23/l l9 A 3,7l 7,130 2/l973Thomburgh [23/119 A [75} Inventors: Charles F. Aquino, Ann Arbor;

Melvin F. Sterner, Bloomfield Hills, Examiner wendeu Bums both ofAssistant Examiner-David D. Reynolds 73] A i Ford company Dearbom,Attorney, Agent, or Firm-R0bert E. McCollum; Keith Mi L. Zerschling 22F1 d: 1 Feb 1974 57 ABSTRACT Appl. No.: 439,457

A carburetor is supplied with an additional fuel and air channelconnected to the engine intake manifold past a movable valve that opensthe channel only when exhaust gases are being recirculated into theengine so that engine driveability is improved. The valve is sensitiveto the movement ofa second valve controlling the recirculation of theexhaust gases as a function of throttle valve movement.

9 Claims, 4 Drawing Figures PATENTEB SEP 1975 SHEET 1 BF 3 PATENTED SE?919??) SHEET 2 UF 3 F'IG.2

SUPPLEMENTAL FUEL SYSTEM FOR EXHAUST GAS RECIRCULATING SYSTEM Thisinvention relates in general to an internal combustion engine exhaustgas recirculating system. More particularly, it relates to one in whicha small amount of additional fuel is added to the intake manifold duringthe recirculation of exhaust gases.

The practice of recirculating exhaust gases into the engine to reducecombustion peak temperatures and pressures and thereby reduce the outputof NO is a well known expedient. However, such recirculation of exhaustgases usually results in reducing engine driveability to a less thansatisfactory level, especially during light acceleration modes ofoperation when the flow rate of recirculated gases is higher. Mostexhaust gas recirculating systems have no provision for compensating fora decrease in driveability other than to make adjustments to other partsof the engine not associated with the exhaust gas flow.

It is a primary object of this invention to add a small amount of fuelto the exhaust gases as they are recirculated into the engine, toimprove engine driveability without increasing the level of emission ofundesirable elements.

It is a further object of the invention to provide an engine exhaust gasrecirculating system that includes a passage between the engine exhaustgas crossover passage that passes beneath the carburetor throttle boresto vaporize the air/fuel mixture, and the engine intake manifold, thepassage containing a valve that is controlled in general as a functionof changes in engine operating modes whereby opening of the valvetriggers a supplemental fuel supply to add a small amount of fuel to theintake manifold in proportion to the flow of exhaust gases, to improveengine driveability.

Other objects, features and advantages of the invention will become moreapparent upon reference to the succeeding detailed description thereof,and to the drawings illustrating the preferred embodiment thereof;wherein,

FIG. 1 is a plan view of a portion of a downdraft type carburetorembodying the invention;

FIG. 2 is a cross-sectional view taken on a plane indicated by andviewed in the direction of the arrows 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view, on a reduced scale, taken on a planeindicated by and viewed in the direc tion of the arrows 33 of FIG. 2;and,

FIG. 4 is a cross-sectional view taken on a plane indicated by andviewed in the direction of the arrows 4-4 of FIG. 1.

FIG. 1, which is essentially to scale, is a plan view of a variable areaventuri carburetor of the downdraft type. It has a pair of rectangularlyshaped induction passages 10, each having one end wall 12 which ispivotally movable and has the profile (FIG. 2) of one-half of a venturi13. Each opposite fixed cooperating wall 14 is formed with the matingprofile of a portion of a venturi. The airflow capacity, therefore,varies in proportion to the opening movement of walls 12 of theinduction passages.

As seen more clearly in FIG. 2, movable walls 12 are pivotally mountedat 15 on a stationary pin. Pivotally attached to each of the wall bodiesis a fuel metering rod or needle 16 that is tapered for cooperation witha main fuel metering jet 18. The needles have a controlled taper toprovide a richer air/fuel mixture at the lower and higher ends of theventuri range. Each jet is located in an aperture inside wall 14 atapproximately the throat or most constricted section of venturi 13. Afuel float bowl or reservoir 20 has a pair of identical passages 22(only one shown) conducting fuel to the main metering jets 18.Downstream of the venturis, the carburetor throttle body portionrotatably mounts a shaft 24 on which are fixed a pair (only one shown)of conventional throttle plates 25 that control the flow of air and fuelthrough induction passages 10.

The size of venturis 13 and the movement of walls 12 is controlled inthis case by a spring returned, control vacuum actuated, diaphragm typeservo 26. The servo consists of a hollow two-piece casting divided intotwo chambers 28 and 30 by an annular flexible diaphragm 32. Thediaphragm is sealingly mounted along its edge in the casting. Chamber 28is an air chamber, connected to ambient or atmospheric pressure througha passage 34. Chamber 30 is a vacuum chamber connected to inductionpassages 10 by a passage P at a point below the throat but still in theventuri 13. This subjects chamber 30 to changes in a control vacuum thatvaries with airflow but at a rate that is slightly different than trueventuri vacuum. The exact location of the tap of course is a matter ofchoice.

Fixed to one side of servo diaphragm 32, by a retainer 34, is a plungeror actuator 36. The plunger is pivotally connected to a shaft 37interconnecting cast portions of the movable walls 12. Fixed to theother side of diaphragm 32 is a retainer 38 against which is seated aspring 39. The other end of the spring bears against a seat 40 axiallyadjustable to vary the spring preload.

The throttle body 42 is flanged as indicated for bolting to the top ofthe engine intake manifold 44, with a spacer element 46 located between.Manifold 44 has a number (only one shown) of vertical risers or bores 48that are aligned for cooperation with the discharge end of thecarburetor induction passages 10. The risers 48 open at their lower endsinto manifold logs or trunks 50 that extend at right angles to therisers for passage of the mixture to the engine intake valves, notshown.

The floor 52 of the intake manifold in this case is heated in a knownmanner by exhaust gases passing through an exhaust gas crossover passage54. The latter passes from the exhaust manifold, not shown, on one s deof the engine to the exhaust manifold on the oppos te side beneath theintake manifold trunks 50 to provide the usual hot spot beneath thecarburetor riser bores to better vaporize the air/fuel mixture.

As best seen in FIG. 3, the spacer 46 is provided with a worm'likerecess 56 that is connected directly to crossover passage 54 in FIG. 2by a bore or passage 58. Also connected to recess 56 is a passage 60containing a flow restricting orifice 61. Passage 60 is alternatelyblocked or connected to a central bore or passage 62 which communicateswith the risers 48 through a pair Of ports 64. Mounted to one side ofthe spacer is a cup shaped boss 66 forming a chamber 68 through whichpassages 60 and 62 are interconnected.

It IS necessary and desirable to provide some sort of control to preventthe recirculation of exhaust gases at undesirable times. For thispurpose, passage 60 normally IS closed by a valve 70 that is moved to anopen Posmml y a er o 72. The servo includes a hollow outer shell 74containing an annular flexible diaphragm 76. The latter divides theinterior into an air chamber 78 and a signal vacuum chamber 80. Chamber78 is connected to atmospheric pressure through a vent 82, while chamber80 is connected to a vacuum signal force through a line 84. The stem 86of valve 70 is fixed to a pair of retainers 88 secured to diaphragm 76.They serve as a seat for a compression spring 90 normally bi asing thevalve to its closed position. The stem slidably and sealingly projectsthrough a plate 92 closing chamber 68.

As shown in FIG. 2, the carburetor contains an exhaust gas recirculating(EGR) port 94 that is located above the closed position of throttlevalve 25 to be traversed by the edge of the throttle valve as it movesopen. The pressure in port 94 thereby varies from atmospheric to themanifold vacuum level as a function of the opening of throttle valve 25.Port 94 is connected to passage 84.

As stated initially, it is desirable when the exhaust gases arerecirculated that a small amount of additional fuel be added to theexhaust gases for better driveability purposes. The construction shownin FIG. 4 provides for the automatic induction of this fuel. Morespecifically, float bowl contains an inverted U-shaped fuel passage 96open at its lower end 98 to the fuel in reservoir 20. At its upper end,the fuel channel is joined to an air bleed passage 100 that opens at itstop through a fixed area orifice 102 to the clean air side of the engineair cleaner, not shown. At its alternate lower end, fuel channel 96 isjoined to a horizontal passage 104 intersecting a vertical passage 106.Passage 106 is connected to the spacer passage 62 (FIG. 3) past a spooltype valve 108. The latter has a pair of spaced lands 110 and 112interconnected by a neck portion 114 of reduced diameter. The latterdefines a channel 115 adapted to register at times with the spacedportions of passage 106 to connect fuel to intake passage 62. The spoolvalve bore 116 is closed by an adjustably mounted plug 117. The plug hasa hollow screw 118 to permit communication of atmospheric pressureagainst the end face of valve land 112. The opposite valve land 110 hasa recess 120 serving as a seat for a spring 122. The spring normallybiases the valve rightwardly to block communication of the intakemanifold vacuum in passage 62 to act on fuel line 106. The screw 118acts as a stop to determine the closed position of the valve 108.Another screw, not shown, can be provided to adjust the preload onspring 122.

As seen in FIG. 4, the left end of bore 116 is connected by a pair ofpassages 124 and 126 to a vacuum signal passage 128 shown in FIG. 3. Thelatter is connected to vacuum passage 60 at a point between the or ifice61 and valve 70 so as to provide a vacuum signal responsive to openingof the valve 70.

In operation, during engine off and idling conditions, throttle valvesare in essentially closed positions thereby providing essentiallyatmospheric pressure in EGR port 94. Accordingly, servo 72 maintainsvalve 86 closed, and no exhaust gas is recirculated from passage 60 topassage 62. The exhaust gas back pressure in line 128, together withspring 122, maintains the fuel metering valve 108 in the position shownin FIG. 4 blocking the fuel line 106.

During part throttle vehicle accelerations, rotation of the throttlevalve to traverse port 94 causes manifold vacuum to be applied to servo72. When the vacuum level is sufficient to overcome the chosen preloadforce of spring 90, valve will open. Exhaust gases will then flow intothe intake manifold runners 50 as controlled by orifice 61.Simultaneously, the suction in line 62 transmitted past valve 70 throughlines 128 and 126 now acts on the end of valve 108. This together withthe atmospheric pressure acting through the screw 118 on the oppositeend of valve 108 moves the valve against the force of spring 122 toconnect the fuel line segment 106 to the intake manifold line 62. Theintake manifold therefore draws fuel through fuel duct 96 together withair through the bleed 100 to the engine cylinders. The added fuel istherefore discharged directly into the exhaust gases.

During wide open throttle accelerations, the manifold vacuum decaysessentially to zero. Therefore, valve 70 will remain closed until themanifold vacuum recovers sufficient to overcome the force of spring andagain recirculate the exhaust gases. Additional fuel and air then alsowill be added in the manner as described above.

From the above, it will be seen that the invention improves enginedriveability during exhaust gas recirculation by supplying a smallamount of additional fuel and air to the engine whenever the exhaustgases are being recirculated, and that because both the EGR andsupplemental fuel are metered by manifold vacuum across a fixed sizeorifice, the flow is essentially proportional to EGR flow.

While the invention has been shown and described in its preferredembodiment, it will be clear to those skilled in the arts to which itpertains that many changes and modifications may be made thereto withoutdeparting from the scope of the invention.

We claim:

1. An exhaust gas recirculating system for an internal combustion enginehaving intake and exhaust manifolding and a carburetor with an inductionpassage connected to the intake manifold and having a throttle valvemovable across the passage to open and close the passage to control theflow therethrough, a duct connecting the intake and exhaust manifoldingfor recirculating the exhaust gases back into the engine, an exhaust gasrecirculating (EGR) control valve movable between alternate positions toopen and close the duct, a vacuum servo having an actuator connected tothe (EGR) valve and having spring means biasing the (EGR) valve to aclosed position, a vacuum signal line connected to the servo for movingthe (EGR) valve to an open position in response to a predeterminedvacuum force acting on the servo, means connecting the vacuum signalline to a port in the induction passage located adjacent the closedposition of the throttle valve to be traversed by the throttle valveduring throttle valve opening movements whereby the signal line fluidforce varies from an essentially atmospheric pressure level at closedthrottle valve positions to manifold vacuum levels in response to thethrottle valve moving above the port, and fuel supply means connected tothe intake manifold to supply fuel into the duct in response to openingof the (EGR) valve providing flow of exhaust gases through the duct.

2. A system as in claim 1, the fuel supply means including a fuel lineconnected to the intake manifold and a control valve in the fuel linenormally blocking the fuel line and moved to open the fuel line inresponse to the induction of exhaust gases through the duct.

3. A system as in claim 1, the fuel supply means including a fuelsource, conduit means connecting the fuel from the source to the intakemanifold, a reciprocable fuel control valve in the conduit means movablebetween first and second positions blocking and unblocking the conduitmeans, spring means biasing the valve to the first position, and secondconduit means connecting the control valve to the duct between the (EGR)valve and exhaust manifolding for movement of the valve to the secondposition in response to flow of gases through the duct.

4. A system as in claim 2, including air supply means connected to thefuel line for the induction of air simultaneous with the induction offuel.

5. A system as in claim 1, the engine including an exhaust gascontaining crossover passage passing beneath the induction passages of acarburetor attached to the engine to warm the passages, the duct beingconnected at one end to the crossover passage, and a pressure tapconnected to the fuel supply means and to the duct between the (EGR)valve and exhaust gas passage for sensing the flow of exhaust gasesthrough the duct upon opening of the (EGR) valve to effect the flow offuel to the intake manifold.

6. A system as in claim 5, the fuel system including a fuel source, aconduit connecting the source to the intake manifold, and a fuel controlvalve in the conduit operably movable in response to the pressure in thetap applied to the control valve upon flow of gases through the duct toopen the second conduit means to flow fuel to the intake manifold.

7. A system as in claim 6, including spring means biasing the controlvalve to a position closing the conduit, the control valve being movedto a position opening the conduit in response to a predeterminedpressure differential between atmospheric pressure acting on one side ofthe control valve and the vacuum signal force of the pressure tap actingon the opposite side.

8. A system as in claim 7, including an air conduit connected to theconduit for the induction of air with fuel.

9. A system as in claim 1, the fuel supply means including a source offuel, a first conduit connecting the source to the intake manifolding, adifferential pressure operated reciprocating fuel control valve in theconduit, spring means acting on one end of the valve biasing it towardsa first position blocking the conduit, means applying atmosphericpressure to act in the opposite direction on the opposite end of thecontrol valve to urge it towards an open position permitting flow offuel to the intake manifolding, a second conduit connecting a portion ofthe duct between the (EGR) valve and the exhaust manifolding to the oneend of the control valve whereby the exhaust gas backpressure in thesecond conduit acting on the control valve during a closed condition ofthe (EGR) valve maintains the control valve blocking flow of fuelthrough the first conduit, opening of the (EGR) valve effecting adifferential pressure acting on the control valve moving it to open thesecond conduit to permit flow-of fuel, the movement of the control valvevarying as a function of the change in pressure of the exhaust gas flow.

1. An exhaust gas recirculating system for an internal combustion enginehaving intake and exhaust manifolding and a carburetor with an inductionpassage connected to the intake manifold and having a throttle valvemovable across the passage to open and close the passage to control theflow therethrough, a duct connecting the intake and exhaust manifoldingfor recirculating the exhaust gases back into the engine, an exhaust gasrecirculating (EGR) control valve movable between alternate positions toopen and close the duct, a vacuum servo having an actuator connected tothe (EGR) valve and having spring means biasing the (EGR) valve to aclosed position, a vacuum signal line connected to the servo for movingthe (EGR) valve to an open position in response to a predeterminedvacuum force acting on the servo, means connecting the vacuum signalline to a port in the induction passage located adjacent the closedposition of the throttle valve to be traversed by the throttle valveduring throttle valve opening movements whereby the signal line fluidforce varies from an essentially atmospheric pressure level at closedthrottle valve positions to manifold vacuum levels in response to thethrottle valve moving above the port, and fuel supply means connected tothe intake manifold to supply fuel into the duct in response to openingof the (EGR) valve providing flow of exhaust gases through the duct. 2.A system as in claim 1, the fuel supply means including a fuel lineconnected to the intake manifold and a control valve in the fuel linenormally blocking the fuel line and moved to open the fuel line inresponse to the induction of exhaust gases through the duct.
 3. A systemas in claim 1, the fuel supply means including a fuel source, conduitmeans connecting the fuel from the source to the intake manifold, areciprocable fuel control valve in the conduit means movable betweenfirst and second positions blocking and unblocking the conduit means,spring means biasing the valve to the first position, and second conduitmeans connecting the control valve to the duct between the (EGR) valveand exhaust manifolding for movement of the valve to the second positionin response to flow of gases through the duct.
 4. A system as in claim2, including air supply means connected to the fuel line for theinduction of air simultaneous with the induction of fuel.
 5. A system asin claim 1, the engine including an exhaust gas containing crossoverpassage passing beneath the induction passages of a carburetor attachedto the engine to warm the passages, the duct being connected at one endto the crossover passage, and a pressure tap connected to the fuelsupply means and to the duct between the (EGR) valve and exhaust gaspassage for sensing the flow of exhaust gases through the duct uponopening of the (EGR) valve to effect the flow of fuel to the intakemanifold.
 6. A system as in claim 5, the fuel system including a fuelsource, a conduit connecTing the source to the intake manifold, and afuel control valve in the conduit operably movable in response to thepressure in the tap applied to the control valve upon flow of gasesthrough the duct to open the second conduit means to flow fuel to theintake manifold.
 7. A system as in claim 6, including spring meansbiasing the control valve to a position closing the conduit, the controlvalve being moved to a position opening the conduit in response to apredetermined pressure differential between atmospheric pressure actingon one side of the control valve and the vacuum signal force of thepressure tap acting on the opposite side.
 8. A system as in claim 7,including an air conduit connected to the conduit for the induction ofair with fuel.
 9. A system as in claim 1, the fuel supply meansincluding a source of fuel, a first conduit connecting the source to theintake manifolding, a differential pressure operated reciprocating fuelcontrol valve in the conduit, spring means acting on one end of thevalve biasing it towards a first position blocking the conduit, meansapplying atmospheric pressure to act in the opposite direction on theopposite end of the control valve to urge it towards an open positionpermitting flow of fuel to the intake manifolding, a second conduitconnecting a portion of the duct between the (EGR) valve and the exhaustmanifolding to the one end of the control valve whereby the exhaust gasbackpressure in the second conduit acting on the control valve during aclosed condition of the (EGR) valve maintains the control valve blockingflow of fuel through the first conduit, opening of the (EGR) valveeffecting a differential pressure acting on the control valve moving itto open the second conduit to permit flow of fuel, the movement of thecontrol valve varying as a function of the change in pressure of theexhaust gas flow.